New synthetic and characterization strategies for polyolefins

Thesis (PhD)--University of Stellenbosch, 2006.ENGLISH ABSTRACT: Metalloxycarbene complexes [(CO)5M1=O(R)M2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*) were synthesized from the reaction between anionic Fischer-type carbene complex salts [(CO)5M1=C(O)R][NEt4] and metallocene chlorides. The molecular and crystal structures of [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] and [(CO)5W=C(Ph)OHf(Cl)Cp2] determined by X-ray methods, show a short Ccarbene-O and relatively long O-Zr and O-Hf separations. Metalloxycarbene complexes in the presence of MAO are active catalysts for homo- and copolymerization of -olefins and produce polymers with heterogeneous properties. 1-Pentene oligomers, homopolymers of ethylene and ethylene/1-pentene copolymers were successfully synthesized using metalloxycarbenes/MAO and the results obtained were critically compared with those synthesized with metallocene/MAO catalysts. The GC and GPC show that 1-pentene oligomers produced with both metalloxycarbenes and metallocenes catalysts range from simple dimers to more complicated high molecular weight (2 600 g/mol) products. The properties of polyethylene and ethylene/1-pentene copolymers were evaluated by, among others, GPC, SEC-FTIR, preparative molecular weight fractionation and HPer DSC. Generally the polymers obtained using metalloxycarbene/MAO catalysts have broad and bimodal molecular weight distributions. The copolymers have higher concentration of 1- pentene in the lower molecular weight fraction than those produced with metallocene/MAO as shown by SEC-FTIR. Consequently, HPer DSC shows a decrease of melting and crystallization temperature towards the low molecular weight fractions.AFRIKAANSE OPSOMMING: Metaaloksikarbeenkomplekse [(CO)5M1=C(R)OM2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*] is gesintetiseer in die reaksie tussen anioniese Fischer-tipe karbeenkomplekssoute, [(CO)5M1=C(O)R][NEt4], en metalloseen dichloriedes. Die molekulêre- en kristalstrukture van [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] en [(CO)5W=C(Ph)OHf(Cl)Cp2] bepaal deur X-straalkristallografiese metodes, toon die aanwesigheid van kort Ckarbeen-O- en relatief lang O-Zr- en O-Hf-bindings. Metaaloksikarbeenkomplekse, in die aanwesigheid van MAO, is aktiewe katalisatore vir die homo- en ko-polimerisering van α-olefiene en is verantwoordelik vir die vorming van polimere met heterogene eienskappe. 1-Penteen oligomere, homopolimere van etileen en etileen/1-penteen ko-polimere is suksesvol gesintetiseer met metaaloksikarbeenkomplekse/MAO en die resultate sodoende verkry, is krities vergelyk met produkte gesintetiseer vanuit metalloseen/MAO prekatalisatore. Die GC en GPC resultate toon dat die 1-penteen oligomere, geproduseer met beide metaaloksikarbeenkomplekse en metallosene, kan wissel van eenvoudige dimere tot meer komplekse, hoë molekulêre massa (2 600g/mol) produkte. Die polietileen en etileen/1- penteen ko-polimere is gekarakteriseer deur onder andere gevorderde, GPC, SEC-FTIR, preparatiewe molekulêre massa fraksionering en HPer DSC. In die algemeen het die polimere verkry met metaaloksikarbeen/MAO katalisatore, breë en bimodale molekulêre massaverspreidings. Die ko-polimere bevat hoër konsentrasies van 1-penteen in die lae molekulêre massa fraksie in vergelyking met dié gevorm vanuit metalloseen/MAO–gekataliseerde mengsels, soos aangedui deur SEC-FTIR-analise. HperDSC wys 'n verlaging in smelt- en kristallisasietemperature in die laer molekulêre massa fraksies

Penta­carbonyl-2κ5 C-chlorido-1κCl-bis­[1(η5)-cyclo­penta­dien­yl](μ-α-oxido­benzyl­idene-1:2κ2 O:C)titanium(IV)tungsten(0)

The title compound, [TiW(C5H5)2(C7H5O)Cl(CO)5], consists of two metal centres, with a (tungstenpenta­carbon­yl)oxy­phenyl­carbene unit coordinated by a titanocene chloride. The oxycarbene group is nearly planar, with the phenyl ring twisted by an angle of 39.1 (2)° with respect to this plane. One of the cyclo­penta­dienyl rings undergoes an offset face-to-face π–π inter­action [3.544 (6) Å] with the symmetry-related cyclo­penta­dienyl ring of a neighbouring mol­ecule

ARIMA forecasts of the number of beneficiaries of social security grants in South Africa

The main objective of the thesis was to investigate the feasibility of accurately and precisely fore- casting the number of both national and provincial bene ciaries of social security grants in South Africa, using simple autoregressive integrated moving average (ARIMA) models. The series of the monthly number of bene ciaries of the old age, child support, foster care and disability grants from April 2004 to March 2010 were used to achieve the objectives of the thesis. The conclusions from analysing the series were that: (1) ARIMA models for forecasting are province and grant-type spe- ci c; (2) for some grants, national forecasts obtained by aggregating provincial ARIMA forecasts are more accurate and precise than those obtained by ARIMA modelling national series; and (3) for some grants, forecasts obtained by modelling the latest half of the series were more accurate and precise than those obtained from modelling the full series.M.Sc. (Statistics)Department of Statistic

A decision support system to assess climate change impacts on rural communities

English: Climate change is likely to affect the way in which people live. Natural resources such as groundwater, surface water and wood form a vital component of the livelihood in rural communities and are used extensively in rural areas where basic services have not yet been provided. The effect of climate change on all these natural resource may impact the lives of those in rural communities. Climate change is already starting to affect some of the poorest and most vulnerable communities around the world. The aim of the dissertation was to develop a framework to assess the vulnerability of rural communities to climate change. This framework used the Millennium Ecosystem Assessment Conceptual Framework as a guideline, but also incorporated the results of face-to-face interviews conducted with members of a selected community. The purpose of the interviews was to interrogate the communities’ level of awareness on climate change and to gain an understanding of the parameters influencing the community’s vulnerability to the effects of climate change. The developed framework allows the calculation of a numerical value which represents the vulnerability of a community to climate change. To illustrate its application, the framework was used to assess the vulnerability of a selected community. In the same way, the framework can be applied to other rural communities in South Africa to assess their vulnerabilities and to prioritise those communities where funds and resources should be allocated when combatting the impacts of climate change. Further work to improve the framework developed in this study is recommended. These recommendations include: 1) considering other existing frameworks to better understand climate change impacts on rural communities and to strengthen and improve the assessment of the vulnerabilities faced by rural communities, 2) expanding the study to include more rural villages in order to better understand how other rural communities are affected by climate change and to establish recommendations which could assist in finding solutions on a wider scale for rural communities that are affected by climate change, 3) including in the framework adaptation measures to protect biodiversity and ecological parameters that support the livelihood of the community, and, 4) including long-term projection of the changes brought on by climate change to refine and improve the framework.Afrikaans: Klimaatverandering sal waarskynlik die manier waarop mense leef affekteer. Natuurlike hulpbronne soos groundwater, oppervlakwater en hout vorm ‘n intrgrale deel van die lewensbestaan van landelike gemeenskappe, en word intens gebruik in landelike areas waar basiese dienste nog nie verskaf is nie. Die effek van klimaatverandering op al hierdie natuurlike hulpbronne mag impakteer op die lewens van mense in landelike gemeenskappe. Klimaatverandering is reeds besig om die armste en mees kwesbare gemeenskappe te affekteer. The doel van hierdie verhandeling was om ‘n raamwerk te ontwikkel om die kwesbaarheid van landelike gemeenskappe tot klimaatverandering te assesseer. Hierdie raamwerk gebruik die Millennium Ecosystem Assessment Conceptual Framework as riglyn, maar inkorporeer oof die resultate van aangesig-tot-aangesig onderhoude met die lede van die gekose gemeenskap. Die doel van die onderhoude was om die gemeenskap se bewustheid rondom klimaatverandering te toets en om ‘n begrip van die parameters te kry wat die kwesbaarheid van gemeenskappe tot klimaatverandering beïnvloed. Die ontwikkelde raamwerk laat die berekening van ‘n numeriese waarde toe wat die kwesbaarheid van die gemeenskap to klimaatverandering verteenwoordig. Om die toepassing van die raamwerk te illustreer, is dit gebruik om die die kwesbaarheid van ‘n geselekteerde gemeenskap te assesseer. Op dieselfde manier kan die raamwerk toegepas word op ander landelike gemeenskappe in Suid-Afrika om hul kwesbaarhede te assesseer en om daardie gemeenskappe te prioriseer waar fondse en hulpbronne toegeken moet word om die impakte van klimaatveradering te beveg. Verder werk om die raamwerk wat in hierdie studie ontwikkel is te verbeter word aanbeveel. Hierdie aanbevelings sluit in: 1) inagneming van ander bestaande raamwerke om die impakte van klimaatverandering op landelike gemeenskappe beter te verstaan, en om die assessering van kwesbaarhede deur landelike gemeenskappe getrotseer te versterk en te verbeter, 2) uitbreiding van die studie om meer landelike dorpies in te sluit sodat beter verstaan kan word hoe klimaat verandering landelike gemeenskappe affekteer en om aanbevelings te maak wat kan help om oplossings op ‘n groter skaal te vind vir landelike gemeenskappe wat geaffekteer word deur klimaatverandering, 3) insluiting in die raamwerk van aanpassingsmeganismes om biodiversiteit, asook die ekologiese parameters wat die lewensbestaan van die gemeenskate ondersteun, te beskerm, en, 4) insluiting in die raamwerk van lang-termynvoorspellings van die veranderinge deur klimaatverandering teweeg gebring om die raamwerk te verbeter en te verfyn

Testing a structural model for demands, resources, engagement and well-being of first-year university students

MA (Industrial Psychology), North-West University, Potchefstroom Campus, 2020The constructs of job demands, job resources as well as engagement and well-being are conceptualised well in literature. Extensive research is available on these constructs in the broader sense of the working environment. However, research is limited regarding first-year students, more especially within the South African context. The present research focused specifically on first-year students at a South African university, testing the following constructs: study demands, study resources as well as student engagement and well-being. The first year at university can often be a difficult phase where students make the transition from a secondary educational institution to the university environment. Therefore, it is vital to investigate the probable predictors of student engagement and success. Information gathered on the influence which study demands and resources have on the engagement and well-being of first-years, could help students and the university improve engagement levels, thus increasing these students’ well-being and success. The objective of this research was to determine significant demands and resources linked to fist-year students’ engagement and well-being. The research investigated how first-year students’ well-being is affected by variations of demands and resources, also when engagement is a mediating factor. Further investigations determined the strength and nature of the relationships between these constructs. The aim of this study was thus to gain a better understanding of the role these constructs play in the life of first-year students in South Africa, as well as the influence of the university environment on student engagement and well-being. A quantitative research approach was followed by using a stratified random sample design, which comprised first-year students at a tertiary institution (N = 773). Product-moment correlations were used to determine the relationships between the constructs. Structural equation modelling was used to analyse the data and test a structural model. The results indicated that study demands have a negative relationship with student engagement, although only academic results confirmed this relationship in the structural model. The findings indicated further that study resources have a positive relationship with student engagement. Through regression analysis, only lecture support and autonomy confirmed the mentioned positive relationship. Personal relationship problems with social and psychological well-being confirmed a negative relationship between study demands and well-being. A positive relationship was confirmed between study resources and well-being by friend support with the various types of well-being; family support with emotional well-being; and autonomy with psychological well-being. In the final phase, engagement was found to mediate the relationship between study demands and well-being negatively, and the relationship between study resources and well-being in a positive sense. Finally, conclusions were drawn from the findings, limitations were discussed and recommendations made for future research and practice.Master

The impact of the National Credit Act (NCA) on the performance of retailers in Sasolburg (Free State Province)

Abstract not availabl

Research funding and modes of knowledge production : a comparison between NRF-funded and industry-funded researchers in South Africa

Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The changing South African policy context since 1994 (new science and innovation policies), and institutional changes at the National Research Foundation (NRF) have had an effect on different funding instruments and related modes of knowledge production. In this study we compare the modes of knowledge production utilized by researchers funded by the NRF and those funded by industry. We also compare the level of scientific productivity of these groups. This study makes two major contributions: first, we provided a reconstruction of the history of research funding in South Africa from 1918 (through the Research Grant Board – RGB), to date (through the NRF established in 1999 as a result of the merger of the Foundation for Research Development (FRD) and the Centre for Science Development (CSD). The second major contribution of this study concerns the relationship between funding sources and modes of knowledge production and dissemination. We found evidence that there is an increase in third stream funding for university research in South Africa. The study shows that respondents who received funding from both the Focus Areas and THRIP, concurrently, produced more average annual research outputs than those who received funding from either the Focus Areas or THRIP only. When we compared respondents who only received the Focus Areas or THRIP grant, we found that those who received the Focus Areas grant published more outputs annually than THRIP-funded researchers, despite the fact that those who received the THRIP grant had larger grant amounts, on average, than their Focus Areas-funded counterparts. We also found that industry/THRIP funding is utilised on problem-solving type of research, i.e. applied research, while public/NRF funding is utilised on basic/fundamental/curiosity-driven research. Overall, the findings show that there is no clear cut conclusion about the influence of funding on the mode of knowledge production. We could not prove that the two factors, that is, funding and mode of knowledge production, are related in a linear fashion. This is a much more complicated situation that requires more investigation.AFRIKAANSE OPSOMMING: Die veranderende Suid-Afrikaanse beleidskonteks sedert 1994 (nuwe wetenskap- en innovasiebeleid), sowel as institusionele veranderinge aan die Nasionale Navorsingstigting (NNS), het 'n uitwerking gehad op verskillende befondsingsinstrumente en verwante vorme van kennisproduksie. In die lig hiervan vergelyk die huidige studie die vorme van kennisproduksie van navorsers wat deur die NNS befonds word met dié van navorsers wat deur die bedryf befonds word. Die twee groepe se onderskeie vlakke van wetenskaplike produktiwiteit word ook vergelyk. Die studie lewer twee belangrike bydraes. In die eerste plek bied dit 'n rekonstruksie van die geskiedenis van die finansiering van navorsing in Suid-Afrika, vanaf 1918 (deur die Navorsingstoekenningsraad), tot en met vandag (deur die NNS wat in 1999 tot stand gekom het met die samesmelting van die destydse Stigting vir Navorsingsontwikkeling – SNO – en die Sentrum vir Wetenskapsontwikkeling – SWO). Die tweede belangrike bydrae van hierdie studie is die ondersoek na die verband tussen befondsingsbronne en verskillende vorme van kennisproduksie en -disseminasie. Die resultate van die ondersoek dui op 'n toename in derdegeldstroom-befondsing wat universiteitsnavorsing in Suid-Afrika betref. Die studie toon verder dat respondente wat befondsing van beide die fokusarea- en THRIP-programme ontvang, se gemiddelde jaarlikse navorsingsuitsette beduidend hoër is as dié van respondente wat slegs binne een van die twee programme befonds word. ʼn Vergelyking van die navorsingsuitsette van respondente wat slegs fokusarea-befondsing ontvang en respondente wat slegs THRIP-befondsing ontvang, toon dat diegene met fokusarea-befondsing se jaarlikse publikasieuitsette gemiddeld hoër is, ondanks die feit dat die THRIP-toekennings groter bedrae behels. Daar is ook gevind dat befondsing deur die bedryf/THRIP gebruik word vir navorsing wat gerig is op probleemoplossing, d.w.s. toegepaste navorsing, terwyl publieke of NNS-befondsing aangewend word vir basiese/ fundamentele/nuuskierigheid-gedrewe navorsing. Die algehele beskouing is dat geen duidelike gevolgtrekking gemaak kan word met betrekking tot die invloed van befondsing op die vorme van kennisproduksie nie. Daar kan nie onomwonde gestel word dat die twee kernfaktore van ondersoek, naamlik befondsing en vorme van kennisproduksie, reglynig met mekaar verband hou nie. Die situasie is meer kompleks en vereis verdere navorsing

An improved model for provision of rural community-based health rehabilitation services in Vhembe District of Limpopo Province, South Africa

PHDRDVInstitute for Rural DevelopmentInstitute for Rural Development and Poverty Alleviatio

Synthesis and characterization of homo- and copolymers of a-olefins using metallocene catalysts

Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: This study comprises the synthesis and characterization of propene/lower a-olefin copolymers and a-olefm homopolymers using metallocene catalyst systems. Incorporation of a-olefin comonomer into the polypropene backbone led to a change in properties such as microstructure and melting and crystallization temperatures. Synthesis of propene/a-olefin (J-butene, l-pentene, l-hexene and 4-menthyl-l-pentene) copolymers was carried out using the Me2Si(2-Methylbenz[e]indenyl)2ZrChIMAO catalyst combination. Copolymers were characterized by NMR, GPC, DSC and CRYSTAF. Comonomer incorporation was generally kept below 6 % to ensure crystallizable copolymers. Comonomer content influences tacticity. It was especially pronounced for propenell-butene copolymers and attributed to the formation of clusters. Melting and crystallization temperatures, (Tm (DSC), Tc (DSC) and Tc (CRYSTAF)), of propene/lower a-olefin copolymers decreased linearly with an increase in comonomer incorporation and strongly depend on comonomer type displaying a different behaviour compared to that of propene/ higher a-olefins (l-octene, I-decene, l-tetradecene, and 1- octadecene) copolymers. The melting and crystallization temperatures of propene/4- methyl-l-pentene copolymers occur between those ofpropene/l-pentene and propenellhexene. Poly-n-olefins (l-pentene, l-hexene, l-octene and l-decene) were prepared using a series of (R-115_C9H6)2ZrChIMAO[R = benzyl, phenyl and Si(CH3)3] and Me2C(115-C5H4-115- C9H6)ZrCh/MAO catalysts under different conditions. The resulting oligomers and polymers were characterized by GPC and NMR. Better conversions were obtained using catalysts with less bulky substituents and high MAO/catalyst ratios. Products ranged from dimeric oligomers to poly-u-olefins with molar masses between ca. 300 g.mol" and 6000 g.mol". Polydispersities, MwlMn, of poly-n-olefins synthesized at room temperatures were approximately 2, however, higher polydispersities were obtained at higher temperatures. Various end groups such as vinylidene, 1,2 disubstituted and 1,1,2 trisubstituted double bonds were observed and attributed to different propagation and termination reactions. The most important vinylidene end group corresponds to a specific 1,2 monomer insertion and termination by p-elimination.AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van propeen/laer-a-olefien kopolimere en a-olefien homo-polimere wat berei is deur van metalloseen-katalisatore gebruik te maak. Die insluiting van 'n a-olefien ko-monomeer in die ruggraat van propileen het 'n verandering in eienskappe soos mikrostruktuur, smelting en die temperatuur van kristallisasie tot gevolg gehad. Die sintese van propeen/a-olefien (l-buteen, I-penteen, I-hekseen en 4-metiel-lpenteen) ko-polimere is uitgevoer met die katalisatorkombinasie Me2Si(2-Metielbenz[e] indeniel)2ZrClzIMAO. Daar is gepoog om die inkorporasie van die ko-monomeer tot <6% te beperk, om sodoende kristalliseerbare ko-polimere te verseker. Die komonomeerinhoud beïnvloed taktisiteit. Dit was veralopvallend in die propeen/l-buteen ko-polimere, en is toegeskryf aan die vorming van trosse (klusters) Die ko-polimere is gekarakteriseer deur van KMR, GPK, DSK en KRISTAF gebruik te maak. Die smelt-en kristallisasie-temperature (Tm (DSC), Tc (DSC) en Tc (CRYSTAF») van die propeen/Iaer-n-olefien ko-polimere het lineêr afgeneem met 'n toename in ko-monomeer inkorporasie en het sterk afgehang van van die tipe ko-monomeer. Die gedrag van laasgenoemde ko-polimere het verskil van dié van die propeenlhoër-a-olefien kopolimere (l-okteen, I-dekeen, I-tetradekeen, en l-oktadekeen). Die smelt- en kristallisasie-temperature van die propeen/4-metiel-l-penteen ko-polimere lê tussen dié van propeen/l-penteen en propeen/l-hekseen. Die poli-a-olefiene (l-penteen, I-hekseen,l-okteen en I-dekeen) is onder verskillende reaksiekondisies berei deur van die katalisatore (R-115-C9H6)zZrChIMAO [R=bensiel, feniel en Si(CH3)3] en Me2C(115-C514-115-C9H6)zrChIMAO.gebruik te maak. Die nuwe oligomere en polimere is met behulp van GPK en KMR gekarakteriseer. Katalisatore met kleiner substituente en hoër MAO/katalisator-verhoudings lewer beter omskakelings. Produkte het gevarieer vanaf dimeriese oligomere tot poli-a-olefiene met molêre massas tussen 300 en 6000 g.mol'. Die polidispersie van die poli-a-olefiene by kamertemperatuur gesintetiseer was ongeveer 2; hoër polidispersies is egter by hoër temperature verkry. Vinilideen, 1.2-disgesubstitueerde- en 1,1,2-trigesubsidueerde dubbelbindings is as eindgroepe waargeneem. Dit is toegeskryf aan verskillende voortplantings- en termineringsreaksies. Die belangrikste vinilideen-eindgroep stem ooreen met 'n spesifieke 1,2 monomeerinvoeging en terminering deur p-eliminasie